The present invention relates to a method for manufacturing a metal interconnection; and, more particularly, to the method for manufacturing the metal interconnection with enhanced filling capability by forming a protection layer on a diffusion barrier layer using a damascene process.
With a high integration of a semiconductor device, a copper interconnection is being applied to the device due to its low electrical resistance. For employing the copper interconnection in the semiconductor device, a damascene process is used because dry-etching process is hardly applied to deposit the copper interconnection.
Referring to FIGS. 1A to 1D, there are provided cross sectional views setting forth a conventional method for manufacturing the copper interconnection by using a damascene process.
The manufacturing steps begin with a preparation of active matrix 110 provided with a conductive layer 112. After this, an insulating layer 114 is formed on top of the conductive layer 112 and then, patterned into a predetermined configuration by using a damascene process, thereby obtaining an opening 116. Thereafter, a diffusion barrier layer 118, e.g., made of titanium/titanium nitride (Ti/TiN), is formed on entire surface including the opening 116 for preventing a penetration of copper atoms into the insulating layer 114.
In a next step as shown in FIG. 1B, a first copper layer 120 is formed on the diffusion barrier layer 118 by using a method such as a physical vapor deposition (PVD) technique at a room temperature.
In a subsequent step as shown in FIG. 1C, a second copper layer is formed on the first copper layer 120 for reflowing copper into the opening 116 by using the PVD technique at a high temperature, thereby obtaining a copper layer 120A. While depositing copper at the high temperature by the PVD technique, the first copper layer 120 reacts with the diffusion barrier layer 118, thereby forming an intermetallic compound 118A. That is, if the diffusion barrier layer is made of Ti/TiN layer, Cu3Ti intermetallic compound is formed between the first copper layer 120 and the diffusion barrier layer 118. The intermetallic compound 118A has a large grain size of Cu3Ti to cause a bad gap-fill property. That is, owing to the large grain size of the intermetallic compound 118A, it plays a role in preventing an adequate deposition in a bottom portion of the opening 116. Thus, a copper layer 120A with a predetermined thickness is formed only over the opening 116 so that there is happened a void 122 between the copper layer 120A and a copper layer 120C, as shown in FIG. 1C.
Finally, a copper layer is polished back to a top surface of the insulating layer, thereby a copper interconnection 120B being remained within the opening 116 as shown in FIG. 1D. Polishing back of the copper layer is accomplished by a chemical mechanical polishing (CMP) technique.
As described above, when the second copper layer is formed at the high temperature after forming the first copper layer at the room temperature, an intermetallic compound having the large grain size may occur on the surface of the diffusion barrier layer.
Therefore, the second copper layer cannot be deposited on sidewalls of the opening so that the void is happened therein and the filling capability is deteriorated. And further, this makes the resistance of the copper interconnection increased and causes a reliability problem of the device at last.
It is, therefore, an object of the present invention to provide a method for manufacturing a copper interconnection with an enhanced filling capability by using a protection layer after forming a diffusion barrier layer using a damascene process.
In accordance with one aspect of the present invention, there is provided a method for manufacturing a metal interconnection, the method comprising the steps of: a) preparing an active matrix provided with a substrate, an insulating layer and an opening formed through the insulating layer; b) forming a diffusion barrier layer on surfaces of the opening and the insulating layer; c) forming a protection layer on the diffusion barrier layer; d) forming a first metal layer into the opening and upon the protection layer; e) forming a second metal layer on the first metal layer; and f) polishing back the first and the second metal layer to a top surface of the insulating layer, thereby forming a metal interconnection.